In an email to those who ordered at least that Space Black version, Apple has clarified that this model will not be in retail stores until all online orders have been fulfilled:

Thank you for ordering an Apple Watch. We’re working hard to ship orders as quickly as possible and in the order they were placed.

As you may have heard, some models of Apple Watch will soon be available for purchase in Apple Retail Stores. We’d like you to know that the model you ordered will not be available for purchase in Apple Retail Stores until all current online orders have shipped.

When your order ships, we’ll send you an email with a specific delivery date and tracking information. For the most up-to-date information about your order, please visit online Order Status.

In other words, don’t cancel your Space Black Apple Watch order with the impression that one can be picked up at an Apple Store two weeks from now.